Roger Federer and his wife, Mirka, described themselves as "incredibly happy" after having their second set of twins.
Boys Leo and Lenny are the latest addition to the Federer family, after the couple had twin girls, Myla Rose and Charlene Riva, four years ago.
“Mirka and I are so incredibly happy to share that Leo and Lenny were born this evening! #TwinsAgain,” Federer posted on Twitter.
The 17-times grand slam singles champion announced earlier on Tuesday that he had withdrawn from this week's Madrid Open Masters event to be alongside his wife at the birth of their children.
“I've decided to withdraw from Madrid to be with my wife Mirka during these next few exciting weeks for our family,” Federer wrote on his Facebook page.
“I apologise to my fans and hope to be back in Madrid next year,” added the 32-year-old, currently ranked four.
“I'll be training near my home, and am excited to rejoin the Tour soon.”
Federer, who won the clay event in the Spanish capital in 2009 and 2012, has not played competitively since last month's Monte Carlo Masters, where he lost to compatriot Stanislas Wawrinka in the final.
Before the birth of Leo and Lenny, he said he would not hesitate to miss any tournament to be at the birth, even the French Open that gets underway on 25 May.
Additional reporting by Reuters